function showTop() {
    var scrollTop = document.documentElement.scrollTop;
    console.log('滚动条位置：' + scrollTop);
}

function debounce(fn, delay) {
    var timer = null;
    return function () {
        if (timer){
            clearTimeout(timer);
        }
        timer = setTimeout(fn, delay);
    }
}
window.onscroll = debounce(showTop, 1000);